The use of strong cationic exchange resins has been disclosed for the separation of fructose and dextrose sugars. In the past, such mixtures were characteristic by-products in the preparation of sucrose from sugar beets or sugar cane. Invert sugar, containing about 50% fructose and 50% dextrose, has been separated by means of liquid chromatography into a fructose-rich portion and a dextrose-rich portion. This process is sometimes called molecular exclusion. Recently, isomerization processes have made possible the commercialization of high fructose corn syrup sweeteners which contains 40-45% fructose, 40-50% dextrose and about 3-8% higher polysaccharides, but such products are not quite as sweet as sucrose. Products containing 55-65% fructose have about the same level of sweetness as sucrose, and can be directly substituted for sucrose in food recipes. The cost of increasing the fructose level higher than about 45% by enzyme treatment accelerates drastically using present commercial processes, so efforts have been made to further increase the fructose content of such sugar mixtures by liquid chromatography.
Chromatographic separation of sugar solutions containing fructose and dextrose has been proposed and used as a means of further increasing the fructose content of fructose/dextrose containing syrups by passing the mixture through an adsorbent resin bed containing a cationic salt of a nuclearly sulfonated, crosslinked polystyrene resin or other adsorbent. When the above named resin is used, fructose has greater affinity than dextrose has for the resin, and the fructose is "held back" in the resin bed, while dextrose passes on through as an effluent stream. The sugar solution and an elution water stream are alternately fed into the resin bed, and the effluent stream contains a dextrose-rich portion followed by a fructose-rich portion which are collected separately. Much effort has been directed towards improving the efficiency of the separation so that it can be scaled up to large volume commercial systems. Flow dynamics through large separation columns must be carefully controlled in order to obtain an optimum separation.